Membrane washing apparatus for flotation device

Abstract

A flotation device (1) which includes a tank (2) to contain a slurry (3) incorporating minerals which are to be extracted. Aeration of the slurry (3) by suitable structure in the device produces a zone (11) of mineralised froth above the slurry (3). A launder (15) directs the mineralised froth away from the tank (2). At least one porous diffusion surface (16) in direct contact with the froth dispenses a washing liquid directly into the froth zone (11).

I claim: 
     
       1. A flotation device comprising: a tank to contain a slurry incorporating minerals to be extracted;   aeration means to aerate the slurry within the tank and thereby produce a zone of mineralised froth above the slurry;   a recovery launder to collect the mineralized froth and to direct said froth away from the tank; and   at least one porous diffusion surface in direct contact with the froth, said diffusion surface being permeable so as to allow a washing liquid to diffuse therefrom into said froth;   
     
     
       2. A flotation device comprising: a tank to contain a slurry incorporating minerals to be extracted;   an aerator to aerate the slurry within the tank and to produce a zone of mineralised froth above the slurry;   a recovery launder to collect the mineralized froth and to direct said froth away from the tank; and   a porous diffusion surface in direct contact with the froth being configured to diffuse a washing liquid into the froth zone and to progressively infuse the froth with wash water permeating through the porous diffusion surface without imparting any substantial kinetic energy to the froth.   
     
     
       3. A flotation device as in claim 1, wherein the diffusion surface includes a flexible porous diffusion membrane mounted on a backing plate. 
     
     
       4. A flotation device as claimed in claim 3, wherein said flexible porous diffusion membrane is substantially permeable only in an expanded condition. 
     
     
       5. A flotation device as claimed in claim 4, further including conduit means to direct the washing liquid under pressure between the diffusion membrane and the backing plate, thereby expanding the membrane into a permeable condition. 
     
     
       6. A flotation device as claimed in claim 5, wherein said membrane is formed from a rubber material. 
     
     
       7. A flotation device as claimed in claim 1, wherein said diffusion surface includes holes at different angles, and wherein the holes at different angles include at least one of round holes or elongated holes. 
     
     
       8. A flotation device as claimed in claim 7, wherein the density of said holes per unit area varies. 
     
     
       9. A flotation device as claimed in claim 1, wherein said diffusion surface defines at least in part an inclined guide surface disposed to direct upwardly migrating froth generally toward the recovery launder. 
     
     
       10. A flotation device as claimed in claim 9, wherein said guide surface is defined by said diffusion surface. 
     
     
       11. A flotation device as claimed in claim 3, wherein said flexible porous diffusion membrane includes reinforcing elements tending to maintain the membrane in a predetermined shape or profile. 
     
     
       12. A flotation device as claimed in claim 1, further including means to introduce additives into the froth via said diffusion surface, to facilitate recovery of selected minerals. 
     
     
       13. A flotation device as claimed in claim 1, further including agitation means in the form of a mixing blade rotatably driven within a surrounding stator via a drive shaft extending into the tank. 
     
     
       14. A flotation device as claimed in claim 13, wherein said aeration means comprises a bore extending axially through said drive shaft to expel pressurised air in the vicinity of the agitation means. 
     
     
       15. A flotation device as claimed in claim 1, wherein said diffusion surface is substantially planar. 
     
     
       16. A flotation device as claimed in claim 1, wherein said diffusion surface is curved. 
     
     
       17. A flotation device as claimed in claim 1, wherein said diffusion surface defines a outer surface extending through the froth zone. 
     
     
       18. A method of recovering minerals from a slurry contained in a tank forming part of a flotation device, said method comprising the steps of: aerating the slurry within the tank and thereby producing a zone of mineralized froth above the slurry;   diffusing a washing liquid directly into the froth zone without imparting any substantial kinetic energy to the froth by means of a porous diffusion surface in direct contact with the froth such that washing liquid infused into the froth progressively washes out entrained gangue material;   collecting the mineralised froth in a recovery launder; and   directing said froth away from the tank via said launder.   
     
     
       19. A method according to claim 18 comprising the further step of directing said washing liquid under pressure between said diffusion surface and an adjacent backing plate to enhance migration of the pressurised washing liquid into the froth zone. 
     
     
       20. A method according to claim 19, wherein said diffusion surface comprises a flexible membrane which is substantially permeable only in an expanded condition, said method comprising the further step of regulating the flow of the washing liquid under pressure between the diffusion surface and the backing plate to expand the membrane into a permeable condition whilst said pressure is maintained, and to allow the membrane to relax into a substantially impermeable condition when said pressure is reduced. 
     
     
       21. A method according to claim 18, comprising the further step of directing the froth toward the recovery launder as it rises within the tank by means of an inclined guide surface defined by said diffusion surface. 
     
     
       22. A method according to claim 18, comprising the further step of introducing additives into the froth via the diffusion surface to facilitate separation of selected minerals. 
     
     
       23. A flotation device comprising: a tank to contain a slurry incorporating minerals to be extracted;   aeration means to aerate the slurry within the tank and thereby produce a zone of mineralised froth above the slurry;   a recovery launder to collect the mineralized froth and to direct said froth away from the tank; and   at least one porous diffusion surface in direct contact with the froth configured for diffusing a washing liquid directly into the froth zone, whereby the washing liquid is introduced into the froth zone without imparting any substantial kinetic energy to the froth and does not collapse or decompose the froth as occurs with conventional spray bar or shower type washing arrangements.